space in html
snippet in html

add spaces html

user6686

   <!-- 1 space -->
 	<!-- tab; 2 space -->
 	<!-- tab; 4 space -->

leading spaces html

user5347

<!--   Add leading white space in front of text  -->

 Hello World

<!--    Output:   ' Hello World'    -->

html space tag

user6576

	non-breaking space	=  
<	less than =	<
>	greater than =	>
&	ampersand =	&

# in html

user3958

# in CSS means your looking at an ID so 
<div class="ExampleClass" id="ExampleID"></div>

#ExampleID would reference the ID
.ExampleClass would reference the class